Condensing boiler, indirect, 4 zones, best way to pipe?

Brian_5

I am installing a Crown condensing boiler 150,000 BTU. I am using a 53 gallon indirect water heater Crown Megastor. The system will have 4 zones. All zones are cast iron radiation. I want this to be a perfect system and a work of art when I am done. I have talked to various people and looked thru many publications about the best way to pipe this system. From what I know it should be piped using a primary secondary method. I would prefer to use the circs and flow checks for controls. Does anyone have a piping diagram about the correct way to pipe this setup. Thank you for any guidance on this?

Chris S

BWC 150

Crown provides a piping diagram, in their manual. You can download it if you don't have the boiler yet. Is that a free standing unit? I was told the new 150's are to be wall mount. At any rate... two closely spaced Ts on the primary loop to your zones, and use their diagram for the DHW with priority. I worked on one yesterday- very nice unit, if installed properly ( this one wasn't)
Chris

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Ted_5

What is the min and max flow rate

of the Crown? Is p/s really needed? Are all the zones the same temp, other then the DHW? What is your location, maybe I could help on the drawing?

Ted

Brad White_185

Buffer Tank

My inclination with any boiler but especially low-mass boilers when micro-zoned or sub-zoned to any extent is to employ a buffer tank, particularly on the return.

(There are several sub-applications such as a reverse-indirect, using a buffer tank as a hydronic decoupler/low loss header or on the supply side as a reservoir from which the zones draw.)

The issue this addresses is essential over-sizing. In other words, if the house were one large zone and was a good fit for the boiler's output, fantastic. The heat loss curve and boiler output curve can be made to match across the season down to the minimum modulation point.

(It will cycle below that but such is the price one pays for more hours at better efficiency; this also underscores the desire to properly size the boiler in the first place without excess.)

Now, when one sub-zones such a system and only one or two zones are calling, you create an inherent over-sizing; the demand is less than the output if all zones were calling as one. Does that make sense?

The buffer tank becomes a "hydronic piggy-bank" (I also call it a "hydronic pole vault"), storing excess capacity which you will have, forestalling boiler cycling inefficiencies and giving you some storage from which to draw while the boiler rests as it will.